[Lustre-discuss] Lustre and iSCSI

[David Pratt]

Hi. Many thanks for your responses. Generally, the qualities of Lustre  
appear great for a Storage Repository for virtual machine images in  
XenServer since you would get a combination of fault tolerance, a  
pretty much infinitely scalable distributed storage pool, speed and  
ability to migrate virtual machines across a number or hosts.  
XenServer can use NFS, iSCSI, NetApp, EqualLogic or Fibre Channel  
storage repositories at this point. It appears there is some  
capability to create a plugin to allow for others. It is possible that  
the only way to get Lustre to work would be with the development of a  
plugin. At this point, to create a minimal Lustre install to play  
with, how many machines will be required?

Regards,
David


On 3-Aug-09, at 8:01 PM, Klaus Steden wrote:

>
> Hi David,
>
> I did some experiments last year with Lustre 1.6.x and a Dell iSCSI
> enclosure. It was a little slow (proof of concept mainly) due to  
> sharing MDT
> and OST traffic on a single GigE strand, but as long as the  
> operating system
> presents a valid block device, Lustre works fine.
>
> hth
> Klaus
>
> On 7/31/09 11:13 AM, "Cliff White" <Cliff.White at Sun.COM> etched on  
> stone
> tablets:
>
>> David Pratt wrote:
>>> Hi. I am exploring possibilities for pooled storage for virtual
>>> machines. Lustre looks quite interesting for both tolerance and  
>>> speed. I
>>> have a couple of basic questions:
>>>
>>> 1) Can Lustre present an iSCSI target
>>
>> Lustre doesn't present target, we use targets, and we should work  
>> fine
>> with iSCSI. We don't have a lot of iSCSI users, due to performance
>> concerns.
>>
>>> 2) I am looking at physical machines with 4 1TB 24x7 drives in  
>>> each. How
>>> many machines will I need to cluster to create a solution with  
>>> provide a
>>> good level of speed and fault tolerance.
>>>
>> 'It depends' - what is a 'good level of speed' for your app?
>>
>> Lustre IO scales as you add servers. Basically, if the IO is big  
>> enough,
>> the client 'sees' the bandwidth of multiple servers.  So, if you know
>> the  bandwidth of 1 server (sgp_dd or other raw IO tools helps) then
>> your total bandwidth is going to be that figure, times the number of
>> servers. This assumes whatever network you have is capable of sinking
>> this bandwidth.
>>
>> So, if you know the IO you need, and you know the IO one server can
>> drive, you just divide the one by the other.
>>
>> Fault tolerance at the disk level == RAID.
>> Fault tolerance at the server level is done with shared storage
>> failover, using linux-ha or other packages.
>> hope this helps,
>> cliffw
>>
>>> Many thanks.
>>>
>>> Regards,
>>> David
>>>
>>>
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>>>
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